REPORT ON THE CRINOIDEA. 317 



theory accounts for the varying conditions of the lowest nodal joint which are presented 

 by different individuals; while the "accident" hypothesis of Filhol's does not explain 

 this fact at all, unless he means that some individuals had Ijecome detached at one time 

 and some at another. But this is precisely what Sir Wyville believed ; only he regarded 

 it as a natural event correspondmg to the separation of the centro-dorsal of a ComatuJa 

 from the rest of the stem below it, which appears to me to be a more rational explanation 

 of the facts than that suggested by FilhoL 



It is possible that the " accident " referred to by the latter author may not mean 

 the fracture of the stem at a syzygy beneath a nodal joint as I have supposed above, 

 but a separation of the stem from its anchorage by the lowest whorl of cirri. This would 

 account for the modification of the nodal joint in the " Porcupine " specimens ; for in the 

 figure which FUhol gives to illustrate the mode of attachment of those dredged by the 

 " Talisman," the lowest nodal joint is represented as not in contact with the rock beneath, to 

 which its cirri are soldered ; so that it might very well have been thickened and rounded 

 in the manner described above. But this supposition, while removing one difficulty, only 

 introduces another. The " Porcupine " specimens were living on a bottom of ooze at a 

 depth of 1095 fathoms, considerably greater than the 1500 metres (800 fathoms) at which 

 the " Talisman " examples were discovered on a rocky or stony bottom. Now in the 

 first place, the cirri could not solder themselves to this ooze with such firmness that they 

 would break rather than loose their hold ; and secondly, there is no trace of such a 

 connection in the cirri borne by the modified lowest nodal joint of any of the " Porcupine " 

 specimens. For in some individuals (PL XIX. fig. l) they are as perfect as those at the 

 nodes above them, and not broken as they were in the detached specimens dredged by 

 the " Talisman." In the case of Rhizocrinus, however, the attachment of the radicular 

 cirri to stones and shells by slight calcareous expansions is well known (PI. X. fig. 15). 



All the Challenger Pentacrinidae, with one exception, were dredged from mud or ooze, 

 and though the stems of several of them terminate below in a rounded nodal joint as in 

 the "Porcupine" examples of Pentacrinus wyville-thomsoni, I have seen no traces of 

 their being attached by the cirri of the lowest whorl soldering themselves to the bottom, 

 as described by the French zoologists. 



The condition of four species of Pentactinus which I have carefully examined vAih. 

 reference to this point appears to me to show conclusively that these observations have 

 by no means the general application which is claimed for them. The internodes oi 

 Pentacrinus ivyville-thomsoni are very long, while the cirri are short (PI. XIX. fig. 1), so 

 that only those of the lowest whorl can come in contact with anythmg beneath the lowest 

 nodal joint. But the case is far difi'erent in many other species, among which I select 

 four for special consideration, as they are represented by individuals in which the lowest 

 whorls of cirri are better preserved than usual. In the present condition of many of the 

 specimens several of the cirri on the stem are more or less broken ; and tliough in the 



